1. Field of the Invention
The present invention relates to an energy storage system for a vehicle having both a compressed gaseous fuel tank and an electric storage battery.
2. Disclosure Information
Vehicles such as hybrid electric vehicles having fuel-burning engines and fuel cell vehicles, both powered by compressed fuel gas such as natural gas or hydrogen, typically utilize generally cylindrical fuel storage tanks. The cylindrical geometry of such tanks is dictated by the relatively high pressures necessary to store an adequate amount of fuel. Needless to say, cylindrical tanks do not package well in automotive vehicles, notwithstanding that engineers have striven for years to achieve acceptable packaging coupled with acceptable vehicle range. The need for packaging an electrical storage battery within either a hybrid electric vehicle or a fuel cell vehicle further compounds the problems faced by vehicle designers. Such batteries are typically not package-efficient and in fact, have frequently been of either a flat construction or square sectional construction, neither which is particularly conducive to packaging within the confines of an automotive vehicle.
The inventors of the present energy storage system have solved many of the problems which plagued known battery and compressed gas storage systems by providing a nesting relationship between an electric storage battery and a generally cylindrical compressed gas storage tank. The geometry of the electric storage battery""s case takes advantage of the geometry found in a conventional automotive vehicle at the forward point of the traditional luggage compartment, by conforming with the seat back bulkhead of the adjacent passenger compartment, while at the same time, the battery case conforms with the cylindrical outer wall of the compressed gas storage tank.
An energy storage system for a vehicle includes a gas storage tank for compressed fuel gas, with the tank having a generally cylindrical outer wall and two arcuate ends, and a generally cylindrical storage battery having a concave surface extending along and nested with at least a portion of the generally cylindrical outer wall of the gas storage tank. The battery preferably further includes at least one additional surface extending parallel to a wall of a vehicular compartment into which the gas storage tank and the storage battery are installed.
The concave surface of the storage battery defines one portion of a generally triangular cross section of the storage battery. The other two portions of the generally triangular cross section are defined by the floor of the storage compartment into which the gas storage tank and storage battery are installed and a segment of the battery""s exterior surface which is generally planar and which is parallel to a seat back bulkhead defining an adjoining passenger compartment.
According to another aspect of the present invention, a storage battery has two generally rectangular ends abutting at least a portion of the arcuate ends of the gas storage tank. The generally rectangular ends include ports allowing the passage of cooling air into the storage battery.
The compartment to which the storage battery and gas storage tank are installed preferably extends laterally across the width of the vehicle body. The storage battery preferably further includes a plurality of battery cell groups, with each group extending axially in a direction parallel to the generally cylindrical outer wall of the gas storage tank. In this manner, the storage battery and the gas storage tank may be tucked into close proximity of the rear seatback of the vehicle, so as to minimum the space occupied by the storage battery and the gas storage tank.
According to another aspect of the present invention, a storage battery further includes a thermal management system for selectively passing either cabin or ambient air through the storage battery.
According to another aspect of the present invention, a method for providing an energy storage system for a vehicle includes the steps of securing a storage battery within a fuel storage compartment immediately adjacent a passenger compartment of the vehicle, with the storage battery having a first exterior surface which is generally planar and which is parallel to a seatback bulkhead defining an adjoining passenger compartment, and a second exterior surface which is concave, with the first and second surfaces combining with the surface which is parallel to the floor of the fuel storage compartment to define a generally triangular cross section of the storage battery. The present method further includes securing a cylindrical compressed fuel gas tank in the fuel storage compartment, with at least a portion of the fuel tank being nested with the concave surface of the storage battery.
It is an advantage of the present invention that an energy storage system according to this invention will allow maximum energy density within the fuel storage space of a hybrid electrical vehicle or fuel cell vehicle. In other words, a maximum amount of electrical charge storage and compressed gas storage will be permitted by the inter-nesting relationship between the storage battery and the gas storage tank.
It is a further advantage of the present invention that the present energy storage system will utilize minimum space within a laterally confined energy storage compartment within a vehicle.
It is another advantage of the present invention that the ability to use ambient air for cooling the storage battery reduces the need for conditioned air drawn from the vehicle""s passenger compartment. This in turn reduces the amount of energy drawn from the battery system to operate a refrigeration system.
It is another advantage that the present system permits maximum bimodal energy storage within a minimum package volume.
Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification.